WASHINGTON — Conservatives have reached the firm conclusion that Hillary Clinton is to blame for those Nigerian schoolgirls kidnapped by the terrorist group Boko Haram, 15 months after she left office.

All they have to do now is fill in the details.

On Fox News last week, Elisabeth Hasselbeck attributed the attack to Clinton’s failure to put the group on a list of foreign terrorist organizations when she was secretary of state. That “perhaps could have saved these girls earlier,” Hasselbeck declared.

Rush Limbaugh, on his radio show, suggested that Clinton didn’t designate the group as terrorist because its members are black.

Fox’s Megyn Kelly floated the idea that Clinton didn’t put the group on the list because doing so would have “angered them,” and a guest on her show said Clinton gave Boko Haram a “green light.”

House Intelligence Committee Chairman Mike Rogers, R-Mich., and others argued that the Twitter campaign raising awareness of the kidnappings, BringBackOurGirls, was evidence of the toothless foreign policy favored by Clinton and President Obama. Clinton, who along with first lady Michelle Obama participated in the campaign, was derided for trying “to fight Boko Haram with hashtags.”

Former House speaker Newt Gingrich called for congressional hearings — which would also provide the opportunity to explore whether Clinton suffered a brain injury, as Karl Rove has alleged, and whether she orchestrated the Monica Lewinsky article in Vanity Fair, as Lynne Cheney suggested.

The nascent effort to pin blame for Boko Haram on Clinton is still far from a full-blown Benghazi conspiracy theory. But it’s worth examining, because it shows how a scandal is born.

The abduction of hundreds of Nigerian girls by Boko Haram, the latest atrocity by the militant group claiming to be acting on Islamic principles, has little to do with the United States. But while the rest of humanity reacts with revulsion, American conservatives have searched for ways to blame the kidnappings on the favorite for the 2016 Democratic presidential nomination.

They found their opening in a decision by the State Department not to put the group on its list of foreign terrorist organizations after Boko Haram bombed U.N. headquarters in Abuja in 2011. The FBI, the CIA and various lawmakers argued for its inclusion, but Nigeria’s government, which Boko Haram is trying to topple, argued against it, as did academic experts on Nigeria.

Opponents figured the designation would elevate the prestige of Boko Haram, which was essentially a domestic Nigerian organization. Instead, Clinton in 2012 put three of the group’s leaders on a list of foreign terrorists. After Boko Haram killed more than 160 civilians in Benisheik, Nigeria, in September 2013, Clinton’s successor, John Kerry, finally put the group on the terror list — and Boko Haram’s brazen attacks continued unimpeded.

The blame-Hillary effort began with a report by a mainstream journalist. After Clinton tweeted about the “unconscionable” abductions and said “we must stand up to terrorism,” Josh Rogin posted an article May 7 in the Daily Beast quoting an anonymous “former senior U.S. official” accusing Clinton of “gross hypocrisy” because she hadn’t put Boko Haram on the list.

From there, conservatives were off to the races.

Inevitably, the accusations landed on the House floor, where Rep. Louie Gohmert, R-Texas, gave a long speech the next day, quoting Rogin’s article, citing Fox News and asserting that Clinton “protected” the terrorists.